1. Field of the Invention
This invention relates to a device arranged to detect the relative movements of a camera and an object to be photographed and to lessen the shaking of an image of the object resulting from the movements.
2. Description of the Related Art
Faulty photographing due to the shaking of a camera has presented a serious problem. In the case of a video camera adapted for taking a motion picture in particular, camera shaking greatly degrades a picture on a monitor or a reproduced picture. To solve this problem, therefore, image stabilization devices of varied kinds have been contrived. One of them is arranged, for example, to stabilize image shakes due to the vibrations of a lens holding hand by utilizing the stability of a rotating gyro. Another known stabilization device is arranged to detect a camera shake with an accelerometer provided on the camera and to move the lens in the direction of offsetting the shake by means of an actuator such as a motor or the like.
Although these known methods may give a good shake correcting effect, they necessitates the use of such a mechanism as the rotating gyro, the accelerometer or the like. Therefore, they are not acceptable for a video camera requiring reduction in size, weight and cost. It is another shortcoming of them that the mere use of such an external sensor having the rotating gyro, accelerometer or the like hardly gives adequate characteristics in terms of responsivity, accuracy, sensitivity, etc.
To eliminate the shortcomings of the above-stated methods, another method has been proposed. In accordance with this method, the relative movements of the camera and an object to be photographed are detected from a sensed image signal obtained by the video camera; and the position of the whole or a part of a lens assembly is shifted in the direction of offsetting an image shake resulting from the relative movements. This method obviates the necessity of the rotating gyro or the accelerometer and is advantageous for reduction in size, weight and cost as the image shake is detected purely in an electronic manner. This method has been disclosed in U.S. Pat. No. 4,788,596 and U.S. patent application Ser. No. 880,152 filed on Jun. 30, 1986.
In accordance with the above-stated method of using the sensed image signal, however, the shaking of the camera is hardly distinguishable from the movement of the object. In cases where the object is moving, the object's movement might be corrected by mistake. Therefore, faulty actions have often been performed to give unnatural pictures.
Other methods for detecting the movement of an object within an image plane, including those not aimed at stabilization of image shakes, have been disclosed in: U.S. Pat. No. 4,678,323 and U.S. patent applications Ser. No. 106,427 filed on Oct. 8, 1987; Ser. No. 154,078 filed on Feb. 9, 1988; Ser. No. 237,511 filed on Aug. 26, 1988; Ser. No. 240,915 filed on Sep. 6, 1988; Ser. No. 264,204 filed on Oct. 28, 1988; and Ser. No. 319,658 filed on Mar. 6, 1989.